1. Field of Invention
The present invention relates to an OLED display panel. More particularly, the present invention relates to a shift register of the OLED display panel.
2. Description of Related Art
With the rapid development of display technology, flat-panel displays have been widely utilized in daily life. Among the flourishing flat-panel displays, active matrix organic light-emitting diode (AMOLED) display is one of the most popular for its high definition, high contrast ratio and the high response speed.
However, under a long-term use, the pixels of the AMOLED panel deteriorate due to aging or unexpected variations from the manufacturing process, causing a mura issue in the AMOLED panel and reducing the display quality.
FIG. 1 is schematic diagram of a pixel compensation circuit in applications. As shown in FIG. 1, the pixel compensation circuit is configured to drive OLED in accordance with the light-emitting signal EM and the scan signals S1 and S2. The pixel compensation circuit includes a light-driving circuit 224 and OLED D1, and the period of the light-emitting signal EM is fixed and double to the scan signals S1 and S2. By using the light-driving circuit 224 to compensate the threshold voltage of the transistor T4, the variations from the manufacturing process are able to be improved. However, the decrease in the luminance of the OLED due to the component aging still exist, particularly in an operation at low gray scale. U.S. Pat. No. 7,414,599, incorporated by reference, discloses the general information about structures and operations of the pixel compensation circuits, and thus are not repeated herein.
In general, the OLED is able to be driven with different light-emitting period, and, at the same time, the driving current is increased to increase the luminance in display, so as to improve the mura issues. However, the light-emitting period is usually fixed in the conventional pixel compensation circuits (e.g., the pixel compensation circuit 100).
Therefore, a heretofore-unaddressed need exists to adjust the light-emitting periods of the OLED in the display with the conventional pixel compensation circuits.